1. Technical Field
The present invention relates in general to an interface module of an asynchronous transfer mode(hereinafter, referring to ATM) terminal using the ATM for transmitting information, particularly to an ATM interface module having an interfacing function required to ATM communication terminals which supports other services and capable of interfacing with the other upper layer service modules by changing an interface module software according to a respective service type.
2. Background
Generally, the ATM terminal using the ATM is consisted of a network connection module unit for connecting to the ATM network, and a service function process module for processing the service to be provided through the terminal. Here, a main processor inside the service function process module unit, controls the network connection module unit and the service function process module unit.
For instance, referring to FIG. 1a, the ATM communication terminal of providing a video on demand service(VODS), comprises a network connection module unit 10 and a service function process module 20. Here, the network connection module unit 10 comprises a physical layer connection unit 10-1, and a physical layer framer/deframer 10-2. And the service function process module 20 comprises a main processor unit 20-1, and an ATM processing unit 20-2, a MPEG(Moving Picture Experts Group)-2 system demultiflexer 20-3, a video processing unit 20-4, an audio processing unit 20-5, and a user interface unit 20-6.
Referring to FIG. 1b, the ATM communication terminal service may be briefly explained when the above terminals are operated. It is assumed that the ATM communication terminals have a same composition in FIG. 1a. 
It is noted that the ATM communication terminal already has a set value for connecting to the ATM network via the user interface. The ATM communication terminal has an allocated channel path for receiving/sending data from/to the video on demand(VOD) server by connecting to the ATM network(in which ATM exchanges are included). And the ATM communication terminal requires a content of the VOD server via the channel path for sending and receives the content of the VOD server data via the channel path for receiving. And a user selects a video title by using the received content and then requires to receive the data to the VOD server via the channel path for sending.
It will be in detail explained how to establish the service processing procedures from the VOD server via the ATM network by followed 3 types.
A first type of procedure is that the channel path is allocated by connecting to the ATM network. A second type of procedure is that a general data is sent/received via sending/receiving paths, and a last type of procedure is that a received MPEG(moving picture experts group)-2 TS(transport stream) is processed.
The VOD server stores the MPEG-2 TS. And the MPEG-2 TS type and a method for mapping the stream to an ATM cells are shown in FIG. 1c. 
In the first type procedure for allocating the channel path by connecting to the ATM network, the ATM communication terminal has a process module for allocating an ATM path in the main processor unit 20-1. The main processor unit 20-1 receives a data and requires a process of a signaling cell to the ATM processing unit 20-2 by composing a payload of a signaling cell, in which the data includes a content which tells that a user wants to connect to the VOD server. The ATM processing unit 20-2 composes a completed signaling cell by inserting a signaling cell header, and then sends the cell to the physical layer framer/deframer unit 10-2. The physical layer framer/deframer unit 10-2 maps the received ATM cells in a payload area which has a frame type commonly used in the physical layer. And the physical layer framer/deframer unit 10-2 inserts an overhead information in the mapped ATM cell according to a content which is initialized in the main processor unit 20-1. Here, the ATM cell having the overhead information is a completed physical layer frame. The physical layer framer/deframer unit 10-2 sends the completed physical layer frame to the physical layer connection unit 10-1. And the physical layer connection unit 10-1 changes the frame to a signal which is commonly used in the ATM network, and sends the signal to the ATM network.
A signal received from the ATM network by passing through an opposite procedure, is converted into a frame type, which is commonly used in the physical layer, through the physical layer connection unit 10-1 by using a deframer function in the physical layer framer/deframer unit 10-2. And then, after selecting the ATM cell in the payload area except the overhead information, the selected ATM cell is sent to the ATM processing unit 20-2. The ATM processing unit 20-2 determines that the received ATM cell includes a signaling data by using an ATM cell header information, sends the payload of the cell to the main processor unit 20-1 in case of including the signaling cell, and then notifies to the main processor unit 20-1 that the cell processing is completed.
The main processor unit 20-1 analyzes the payload of the received cell with a data in order to interface with the VOD server, in which the data may be used for setting a channel for receiving/sending from/to the VOD server. Here, a channel which receives the MPEG data, is commonly differentiated from a channel which receives the general data. And also it is common that a channel path for sending is allocated.
In the second type procedure of sending/receiving the general data via the sending/receiving path, a receiving process is the same as the first type in composing the signaling cell. Here, it is the same that when the header information of the ATM cell is sent, the channel path which is allocated in the signaling cell process unit, is used. And also it is same that when the ATM cell received from the ATM processing unit 20-2, is processed, the channel path which is allocated from the signaling cell processing unit is used. When the general data is sent/received, the same data structure as used in the VOD server is generally used.
In the last type procedure of processing the received MPEG-2 TS, the ATM processing unit 20-2 sends the payload area of the ATM cell header information except the header to the main processor unit 20-1, after mapping the MPEG-2 TS in the ATM cell payload and sending the mapped MPEG-2 TS to the ATM terminal. The main processor unit 20-1 analyzes whether the payload processed from the ATM processing unit 20-2, is the signaling cell, the general data, or the content including the MPEG-2 TS by using the content processed from the ATM processing unit 20-2.
The main processor unit 20-1 stores the content including the MPEG-2 TS, temporarily. And the main processor unit 20-1 selects the MPEG-2 TS only, and then sends the selected stream to a MPEG-2 system demultiflexer 20-3. The MPEG-2 system demultiflexer 20-3 analyzes the received MPEG-2 TS and separates the MPEG-2 TS into a video stream and an audio stream. And the MPEG-2 system demultiflexer 20-3 sends the video stream to a video process unit 20-4 and the audio stream to an audio process unit 20-5 respectively, in order that the user may watch the video.
The main processor unit 20-1 is easy to be overloaded because of initiating the physical layer framer/deframer unit 10-2, the ATM processing unit 20-2, the MPEG-2 system demultiflexer 20-3, the video processing unit 20-4, the audio processing unit 20-5, and the user interface unit 20-6, and have a service process module function which is required by each process module. Accordingly, high capacity processor should be required. And also there are disadvantages, such that the network connection module unit and an upper service processing module unit are composed respectively and it is united to one processor after the overall shape is changed when the upper layer service which is applied by the above structure, is changed.
Further information on an adapter for interfacing the ATM network can be found in copending U.S. Pat. No. 5,548,587, entitled xe2x80x9cAsynchronous transfer mode adapter for desktop applicationsxe2x80x9d, which is incorporated by reference herein.
But, the conventional ATM communication terminal is designed in order to control the ATM interface function by a corresponding control device. Therefore, there are problems that a hardware/software of a single type ATM terminal should be changed for interfacing with the service module of other different upper layer in case of developing the single type ATM terminal which may provide for the other services. Consequently, it takes so much time to develop a hardware/software for the single type ATM terminal.
Accordingly, the present invention is provided to solve the problems. The present invention has an independent module in order to process, by adding an ATM processing unit on the network connection module unit which is connected to the ATM network, controlling the ATM process unit with an extra processor, and separating the upper layer and the ATM layer. Thereby, an object of the present invention is to provide an ATM interface module capable of using the conventional service processing functions by using the ATM network. And it is established by using the interface between the upper layer and the ATM layer with last input/output, in which the last input/output are commonly used in the upper layer, even though the ATM interface module does not know how to process the ATM in the service function process module provided in the upper layer.
One embodiment of the present invention to achieve the object provides an ATM interface module comprising an ATM layer processing means for outputting a useful ATM cell payload(SAR-PDU: segmentation and reassembly protocol data unit) to the control interface means after selecting the SAR-PDU area by using a header information in the ATM cell which is from the physical layer interface unit and inserting an ATM cell header information after separating a data(CS-PDU: convergence sublayer protocol data unit) to the SAR-PDU, and outputting an ATM cell, in which the ATM cell is a SAR-PDU including the header information and in which the CS-PDU is for sending to an external ATM network, a physical layer interface means for mapping the ATM cell applied from the ATM layer processing means, in a payload area of the physical layer frame commonly used in the external ATM network, or for selecting an ATM cell from the physical layer frame payload area applied from the ATM network and the selected ATM cell to the ATM layer processing means, and a control interface means for converting the several SAR-PDUs into a U-SDU(user service data unit), in which the U-SDU includes a data required from the upper layer service process module or an upper layer service control protocol data, and outputting the U-SDU or for converting the U-SDU applied from the upper layer service process module into a certain data format for processing to the ATM cell in the ATM layer processing means and outputting the certain data format to the ATM layer processing means.
Another embodiment of the present invention to achieve the object provides an ATM interface module, comprising an ATM layer processing means for outputting a SAR-PDU to the control interface means after selecting the SAR-PDU area by using a header information in the ATM cell which is from the physical layer interface means and inserting an ATM cell header information after separating a CS-PDU to the SAR-PDU, and outputting an ATM cell, in which the ATM cell is a SAR-PDU including the header information and in which the CS-PDU is for selecting to an external ATM network, a physical layer interface means for mapping the ATM cell applied from the ATM layer processing means in a payload area of the physical layer frame commonly used in the external ATM network, or for selecting an ATM cell from the physical layer frame payload area applied from the ATM network and the selected ATM cell to the ATM layer processing means, and a control interface means for controlling the ATM layer processing means in order to determine that the ATM cell payload applied from the ATM layer processing means is for an ATM network connection or for an external host, and for selecting and maintaining a parameter for a network connection from the ATM cell payload applied from the ATM layer processing means after generating a control data for a network connection to the SAR-PDU format.
The present invention includes the physical layer interface means comprising a physical layer connection unit for sending/receiving a frame which is including the ATM cell by matching with the ATM network, and a physical layer framer/deframer unit for mapping the ATM cell which is applied from the ATM layer processing means, in a payload area of the frame which is commonly used in the physical layer and outputting the mapped ATM cell or for selecting the ATM cell in the payload area of the frame applied from the physical layer connection unit and outputting the selected ATM cell to the ATM layer processing means.
The present invention includes the ATM layer processing means comprising a first memory unit for storing a data which is applied from the control interface means for sending to an external ATM network and an ATM processing unit for selecting an ATM cell payload(SAR-PDU) area after selecting a useful ATM cell by using a header information in the ATM cell which is from the physical layer interface means and outputting the SAR-PDU to the control interface means, or inserting an ATM cell header information after separating a data(CS-PDU: convergence sublayer protocol data unit) stored in the first memory unit to the SAR-PDU, and outputting the ATM cell to the physical layer interface means.
The present invention includes the control interface means comprising a second memory unit for storing the ATM cell payload(SAR-PDU) applied from the ATM layer processing unit, and a control processor unit for converting a CS-PDU into a U-SDU(user service data unit) after converting the several SAR-PDUs stored in the second memory unit into the CS-PDU format, in which the U-SDU includes a data required from the upper layer service process module or an upper layer service control protocol data, and outputting the U-SDU or for converting the U-SDU applied from the upper layer service process module, into a certain data format(CS-PDU) for processing to the ATM cell in the ATM layer processing means and outputting the CS-PDU to the ATM layer processing means.